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SarkariResultOutBMS · 2024

Previous Year Question

Which of the following is a semi-controlled semiconductor device?
  1. Gate turn-OFF thyristor
  2. Silicon-controlled rectifier
  3. Metal-oxide FET
  4. Insulated-gate bipolar transistor

Correct answer: B

Explanation

An SCR is semi-controlled because its gate controls turn-on, but the gate cannot normally force it off. Once latched, an SCR turns off only when anode current falls below the holding current or reverse voltage/commutation is applied.

Formula

SCR: gate-controlled turn-on; turn-off by current extinction/commutation

Step-by-step solution

Semi-Controlled Device explanatory diagram

Correct Answer

B — Silicon-controlled rectifier

Concept and Reasoning

An SCR is semi-controlled because its gate controls turn-on, but the gate cannot normally force it off. Once latched, an SCR turns off only when anode current falls below the holding current or reverse voltage/commutation is applied.

Calculation / Key Relation

SCR: gate-controlled turn-on

turn-off by current extinction/commutation

Exam Takeaway

Semi-controlled means control over turn-on but not normal gate turn-off.

Common Mistake

Do not group fully gate-controlled devices such as MOSFET/IGBT with the SCR.

Common mistake

Do not group fully gate-controlled devices such as MOSFET/IGBT with the SCR.

Exam tip

Semi-controlled means control over turn-on but not normal gate turn-off.

Quick method

Semi-controlled means control over turn-on but not normal gate turn-off.